Radiation is not only related to daily life, but also omnipresent. Cosmic rays and surface radiation existed in natural environment collectively referred to as natural environmental background radiation, which will vary according to terrain and geology. In addition to natural background radiation, radiation sources caused by human factors have a variety of applications of radiation on people's livelihood, wherein the medical radiation applications of radiation diagnosis, radiation therapy and nuclear medicine are the most common.
The principle of radiation therapy is mainly the use of high-energy radiation, usually indirect ionizing radiation, acting with the tumor cells so that the tumor cells are ionized or excited to produce toxic free radicals, which in turn cause cell damage; or the radiation energy released by direct ionizing radiation causing single or double helix break in DNA of the cancer cells. Regarding the treatment prescription dose, the physician is able to confirm the feasibility of the treatment and the expected therapeutic effect, based on a detailed assessment of the radiation doses received by malignant tumor and normal tissue according to the complex treatment plan. When the treatment team confirms the treatment plan, the irradiation parameters of the treatment plan will be delivered to the treatment instrument. With regular beam quality assurance operations, the difference between the dose received by the patient and the prescription dose of the treatment plan is determined to be less than the error range tolerated by the clinical treatment. The patient completes the treatment after a series of irradiation. The principle of radiation therapy is based on radiation damage theory in radiation biology. It is known from radiation dose-tissue volume curve that middle section of the curve has the largest slope, at where if the dose changes 5%, it can affect the tumor control rate by 10% to 20%, and will likely cause the chance of normal tissue complications to be as high as 20% to 30%. So the most important part of radiotherapy is to give the correct prescription dose.
Modern medical radiotherapy equipments are mostly high-energy electronic linear accelerator, such as high-energy X-ray therapy machine; In addition, heavy charged particle radiation therapy technology for example proton therapy, carbon ion therapy and others also begins to flourish, showing that radiation therapy technology can indeed be used as a weapon against malignant tumors. Therefore, radiotherapy techniques need to be combined with more prudent quality assurance measures and dose validation programs to ensure the quality of the patient's treatment.
However, when faced with a mixed radiation field composed of a variety of radiations, the mixed radiation field of neutrons and gamma rays generated by the boron neutron capture therapy system is taken as an example (not limited thereto). Dose measurement of boron neutron capture therapy beam is an important issue in clinical treatment, and its difficulty lies in the need to be able to effectively distinguish the dose caused by the different radiation. Commonly used measurement tools such as paired ionizing chamber and thermoluminescent dosimeter cannot perform dose measurement in a wide range over a short period of time. However, in practice, in radiotherapy beam quality assurance or treatment plan validation, a two-dimensional planar dose distribution must be used to thoroughly evaluate the beam characteristics and the quality of the treatment plan. Therefore, it is necessary to propose a radiation dose measuring method for the mixed radiation field.
The statements in this section merely provide background information related to the present disclosure and may not constitute prior art.